Solid-state sensors and particularly biosensors have received considerable attention lately due to their increasing utility in chemical, biological, and pharmaceutical research as well as disease diagnostics. In general, biosensors consist of two components: a highly specific recognition element and a transducing structure that converts the molecular recognition event into a quantifiable signal. Biosensors have been developed to detect a variety of biomolecular complexes including oligonucleotide pairs, antibody-antigen, hormone-receptor, enzyme-substrate and lectin-glycoprotein interactions. Signal transductions are generally accomplished with electrochemical, field-effect transistor, optical absorption, fluorescence or interferometric devices.
It is known that the intensity of the visible photoluminescence changes of a porous silicon film depend on the types of gases adsorbed to its surface. Based on this phenomenon, a simple and inexpensive chemical sensor device was developed and disclosed in U.S. Pat. No. 5,338,415.
As disclosed in that patent, porous films of porous films of silicon (Si) can be fabricated that display well-resolved Fabry-Perot fringes in their optical reflectance properties. The production of a porous silicon (Si) layer that is optically uniform enough to exhibit these properties may be important for the design of etalons (thin film optical interference devices for laser spectroscopy applications) and other optical components utilizing porous Si wafers. Such interference-based spectra are sensitive to gases or liquids adsorbed to the inner surfaces of the porous Si layer.
Ever increasing attention is being paid to detection and analysis of low concentrations of analytes in various biologic and organic environments. Qualitative analysis of such analytes is generally limited to the higher concentration levels, whereas quantitative analysis usually requires labeling with a radioisotope or fluorescent reagent. Such procedures are time consuming and inconvenient. Thus, it would be extremely beneficial to have a quick and simple means of qualitatively and quantitatively detect analytes at low concentration levels. The invention described hereinafter provides one such means.